Neurovascular lesions are insidious and unpredictable. While there have been notable recent advances in minimally invasive access to these lesions using advanced micro-catheter systems, there is a paucity of equally high performing embolization materials that can be delivered through these catheters to effectively treat clinically challenging lesions. The overall goal of this project is to further develop a highly promising new hydrogel material for the endovascular treatment of aneurysms. This material, ALGEL-II(r), is an ultrapure alginate that is non-adhesive, injectable, mechanically stable, and biocompatible. Prior phases of this commercialization effort have resulted in successful pre-clinical studies and an IDE application to the FDA to begin clinical trials on ALGEL for embolization of arteriovenous malformations. The goal is to accomplish the next steps towards commercialization. Specific Aim 1 is to conduct materials testing of ALGEL-II to assess long-term stability and biocompatibility in small-neck aneurysms. This aim is directed at manufacturing clinical-grade ALGEL and completing FDA-standard long-term toxicity studies in mice and the required panel of genotoxicity studies. The final milestone of this aim is submission of an IDE application to the FDA for a Phase I clinical trial. Specific Aim 2 is to develop clinically appropriate techniques for using ALGEL to embolize wide-neck and bifurcation aneurysms. The studies will adopt a new animal model in dogs and compare the treatment and healing response to that previous found in swine. This project is based on a solid foundation of research and development in the clinical use of ALGEL for treating a wide range of neurovascular defects. The project team includes a core group of physicians, consultants, suppliers, and business alliances that has the technical, medical, and business expertise to make this project successful.